Field of the Invention
The present invention relates to image generation methods and apparatuses, and in particular to the generation of images by post-processing techniques, from existing image data, for stereoscopic display applications.
Stereoscopy in three-dimensional (3-D) graphics refers to techniques for delivering different but correlated images to the left and right eyes in order to stimulate the perception of depth: a number of such techniques are described in "Computer Graphics: Principles and Practice" by James D. Foley et al, 2nd Edition, published by Addison-Wesley 1990, ISBN 0-201-12110-7 at pages 915 to 917. Typically, one 3-D graphics renderer generates the image for the left eye and another generates the image for the right eye. These images might then be fed to a Head Mounted Display or similar stereoscopic display device. There are also multiple view autostereoscopic display devices such as the Philips 3D LCD where, instead of separate images for each of two viewpoints there are in general N images respectively for N viewpoints. Dedicating one 3-D graphics renderer to rendering each image can become expensive, and time multiplexing a renderer is often impractical because such a renderer is typically used to capacity in rendering one image per frame period in order to provide for smooth motion.
To avoid such drawbacks, so-called synthetic stereoscopy may be used: in a simple stereoscopic application where respective images are required for the left and right eyes, pixels in the original image can be shifted to the left or right as a function of their distance from the viewer (expressed as their depth) to synthesise left and right images which rely on the parallax introduced by the shifting to stimulate perception of depth. Whilst the technique is cheaper than providing a separate renderer per view, it suffers from gaps created in the images where pixels have been shifted to the left or right. Rendering a central image and shifting to obtain left and right images creates smaller gaps than rendering for example the left eye image and shifting to generate the right eye image, but the latter requires less resources.